Field of the Invention
The present invention relates to a method for fabricating stacked vias or electrical plated-through holes stacked one above the other for microelectronic components. A known configuration is disclosed in U.S. Pat. No. 5,710,462.
U.S. Pat. No. 5,328,553 describes a method for filling the contact holes.
Nowadays it is generally customary to provide a plurality of wiring planes in microelectronic components, the planes each being isolated from one another by intervening insulating layers. In order to connect together two wiring planes lying one above the other or to establish a contact between the first wiring plane and the microelectronic structures lying underneath, before the top wiring plane is applied, a through hole is formed in the intervening insulating layer and is filled with a conductive material. The top wiring plane is then applied and patterned.
If two wiring planes which do not lie directly one above the other are to be connected to one another, or if the microelectronic structures lying below the first wiring plane are to be connected directly to the second wiring plane, i.e. at least one further wiring plane lies in between, a stacked via is usually provided, as is explained in more detail below.
What has turned out to be disadvantageous in the case of the prior art is the fact that the metal area of a metal landing pad has to be made large enough that a lower via is definitely covered by it, or an upper via definitely lands on it.
Since this configuration is associated with a large space requirement, attempts are made to use smaller metal landing pads, thereby giving rise to the risk of the upper via reaching the side edge of the pad and the subsequently sputtered liner not being tight on account of pitting in the metal or dielectric. In particular, such small metal areas are difficult to reach in terms of resist engineering, which necessitates complicated and costly resist techniques or entails the risk of increased defect densities due to resist plugs tilting over.
Although the problem of the vias meeting the metal side edges with a non-tight liner can be supplemented by making the metal landing pads appropriately large, this entails a high space requirement. Liner deposition by sputtering can also be replaced by more expensive chemical vapor deposition (CVD).